Crystal Structure, Stability and Desolvation of the Solvates of Sorafenib Tosylate

Injectable In-Situ Forming Depot Based on PLGA and PLGA-PEG-PLGA for Sustained-Release of Risperidone: In Vitro Evaluation and Pharmacokinetics in Rabbits

In the current research, novel drug delivery systems based on in situ forming gel (ISFG) (PLGA-PEG-PLGA) and in situ forming implant (ISFI) (PLGA) were developed for one-month risperidone delivery. In vitro release evaluation, pharmacokinetics, and histopathology studies of ISFI, ISFG, and Risperdal CONSTA^® were compared in rabbits. Formulation containing 50% (w/w %) of PLGA-PEG-PLGA triblock revealed sustained release for about one month. Scanning electron microscopy (SEM) showed a porous structure for ISFI, while a structure with fewer pores was observed in the triblock. Cell viability in ISFG formulation in the first days was more than ISFI due to the gradual release of NMP to the release medium. Pharmacokinetic data displayed that optimal PLGA-PEG-PLGA creates a consistent serum level in vitro and in vivo through 30 days, and histopathology results revealed nearly slight to moderate pathological signs in the rabbit's organs. The shelf life of the accelerated stability test didn't affect the results of the release rate test and demonstrated stability in 24 months. This research confirms the better potential of the ISFG system compared with ISFI and Risperdal CONSTA^®, which would increase patients' compliance and avoid problems of further oral therapy.

Exploring the thermal behaviour of the solvated structures of nifedipine

Understanding the solvation and desolvation of pharmaceutical materials is an important part of materials discovery and development. In situ structural data are vital to understand the changes to crystal form that may occur in the system. In this study, the isolation and characterization of seven solvates of the L-type calcium channel antagonist, nifedipine, is described using variable-temperature powder X-ray diffraction so that the structural evolution as a function of temperature can be followed. The solvates reported herein can be split into those that are structurally similar to the previously reported dimethyl sulfoxide (DMSO) and dioxane solvates and those that have a novel packing arrangement. Of particular note is the solvate with tetrahydrofuran (THF) which has a hydrogen-bonding motif between the nifedipine molecules very similar to that of metastable β-nifedipine. In addition to variable-temperature X-ray diffraction, the stability of the solid forms was assessed using differential scanning calorimetry and thermogravimetric analysis and indicates that in all cases desolvation results in the thermodynamically stable α-polymorph of nifedipine even with the THF solvate. From the diffraction data the pathway of desolvation during heating of the DMF solvate showed conversion to another likely 1:1 polymorph before desolvation to α-nifedipine. The desolvation of this material indicated a two-stage process; first the initial loss of 90% of the solvent before the last 10% is lost on melting. The methanol solvate shows interesting negative thermal expansion on heating, which is rarely reported in organic materials, but this behaviour can be linked back to the winerack-type hydrogen-bonding pattern of the nifedipine molecules.

Photonic and magnetic materials for on-demand local drug delivery

Nanomedicine has been considered a promising tool for biomedical research and clinical practice in the 21st century because of the great impact nanomaterials could have on human health. The generation of new smart nanomaterials, which enable time- and space-controlled drug delivery, improve the limitations of conventional treatments, such as non-specific targeting, poor biodistribution and permeability. These smart nanomaterials can respond to internal biological stimuli (pH, enzyme expression and redox potential) and/or external stimuli (such as temperature, ultrasound, magnetic field and light) to further the precision of therapies. To this end, photonic and magnetic nanoparticles, such as gold, silver and iron oxide, have been used to increase sensitivity and responsiveness to external stimuli. In this review, we aim to report the main and most recent systems that involve photonic or magnetic nanomaterials for external stimulus-responsive drug release. The uniqueness of this review lies in highlighting the versatility of integrating these materials within different carriers. This leads to enhanced performance in terms of in vitro and in vivo efficacy, stability and toxicity. We also point out the current regulatory challenges for the translation of these systems from the bench to the bedside, as well as the yet unresolved matter regarding the standardization of these materials.

Sorafenib tosylate incorporation into mesoporous starch xerogel for in-situ micronization and oral bioavailability enhancement

Poorly water-soluble drugs like sorafenib tosylate (SFB) can be made more soluble and orally bioavailable using a biocompatible hydrophilic matrix yields amorphous or microcrystalline drugs with high stability and low recrystallization risk. Mesoporous starch (MPS) due to its edibility, biodegradability, high surface area, and confined pores. In this study, MPS, either alone or in combination with polyvinylpyrrolidone (PVP), was employed for improving SFB oral bioavailability. To this aim, MPS was prepared in three steps: gelatinization, solvent exchange, and vacuum drying, after which it was used to incorporate SFB at various ratios using the immersion/solvent evaporation technique. Nitrogen adsorption/desorption analysis, Fourier transform infrared spectrometry (FTIR), field emission scanning electron microscopy (FE-SEM), powder X-ray diffraction (XRD) crystallography, and differential scanning calorimetry (DSC) were used to characterize SFB-loaded and drug-free samples, which confirmed the successful preparation of mesoporous structures with desirable uniform porosity, small pore size (about 5.3 nm), and specific surface area of about 24 m²/g. In-vitro dissolution testing revealed that the SFB dissolution rate increased substantially for the loaded MPS or MPS-PVP samples. Furthermore, when SFB was loaded in MPS-PVP, single-dose pharmacokinetics in rats confirmed an enhanced oral absorption kinetic. Therefore, impregnation of poorly soluble drugs such as SFB in the PVP-modified MPS excipient, which is constructed from a combination of mesoporous materials and a drug recrystallization inhibitor such as hydrophilic polymers, is proposed as a promising strategy for desirable enhancements in drug solubility, oral bioavailability, and efficacy.

Polymorphic solvates, ionic cocrystals and C–N bond formation to form ionic cocrystals in sulfamethoxazole and sulfathiazole-derived urea

Solvates and ionic cocrystals of two sulfa-drug based urea derivatives were studied, where also polymorphs of a solvate, thermal stability, unusual C–N bond formation and desolvation were elucidated.

Impact of Crystal Habit on the Dissolution Rate and In Vivo Pharmacokinetics of Sorafenib Tosylate

The dissolution rate is the rate-limiting step for Biopharmaceutics Classification System (BCS) class II drugs to enhance their in vivo pharmacokinetic behaviors. There are some factors affecting the dissolution rate, such as polymorphism, particle size, and crystal habit. In this study, to improve the dissolution rate and enhance the in vivo pharmacokinetics of sorafenib tosylate (Sor-Tos), a BCS class II drug, two crystal habits of Sor-Tos were prepared. A plate-shaped crystal habit (ST-A) and a needle-shaped crystal habit (ST-B) were harvested by recrystallization from acetone (ACN) and n-butanol (BuOH), respectively. The surface chemistry of the two crystal habits was determined by powder X-ray diffraction (PXRD) data, molecular modeling, and face indexation analysis, and confirmed by X-ray photoelectron spectroscopy (XPS) data. The results showed that ST-B had a larger hydrophilic surface than ST-A, and subsequently a higher dissolution rate and a substantial enhancement of the in vivo pharmacokinetic performance of ST-B.

Structural Polymorphism of Sorafenib Tosylate as a Key Factor in Its Solubility Differentiation

The presence of active pharmaceutical ingredients (APIs) in the forms of different polymorphic states can induce differences in their physicochemical properties. In the case of poorly soluble APIs, like the oncological drug sorafenib tosylate, small variations in solubility may result in large bioavailability differences. The control of its therapeutic dose is crucial from the effective pharmacotherapy point of view and the reduction of side effects. Therefore, this study aimed to assess the influence of sorafenib tosylate polymorphic forms on its solubility and, consequently, permeability, based on passive diffusion through membranes simulating the gastrointestinal tract (GIT) conditions. In the first part of the work, two crystalline forms of sorafenib tosylate were identified using the X-ray powder diffraction, FT-IR, and Raman spectroscopy. Subsequently, solubility studies were carried out. Both forms of sorafenib tosylate were insoluble in 0.1 N hydrochloric acid (HCl), in acetate buffer (pH 4.5), and in phosphate buffer (pH 6.8). Solubility (mg/mL) of form I and III of sorafenib tosylate in 0.1 N HCl + 1.0% SDS was 0.314 ± 0.006 and 1.103 ± 0.014, respectively, in acetate buffer pH 4.5 + 1.0% SDS it was 2.404 ± 0.012 and 2.355 ± 0.009, respectively, and in phosphate buffer pH 6.8 + 1.0% SDS it was 0.051 ± 0.005 and 1.805 ± 0.023, respectively. The permeability study was assessed using the parallel artificial membrane permeability assay (PAMPA) model. The apparent permeability coefficient (P_app—cm s⁻¹) of form I and III in pH 1.2 was 3.01 × 10⁻⁵ ± 4.14 × 10⁻⁷ and 3.15 × 10⁻⁵ ± 1.89 × 10⁻⁶, respectively, while in pH 6.8 it was 2.72 × 10⁻⁵ ± 1.56 × 10⁻⁶ and 2.81 × 10⁻⁵ ± 9.0 × 10⁻⁷, respectively. Changes in sorafenib tosylate concentrations were determined by chromatography using the high-performance liquid chromatography (HPLC)–DAD technique. As a result of the research on the structural polymorphism of sorafenib tosylate, its full spectral characteristics and the possibility of using FT-IR and Raman spectroscopy for the study of polymorphic varieties were determined for the first time, and the HPLC method was developed, which is appropriate for the assessment of sorafenib solubility in various media. The consequences of various physicochemical properties resulting from differences in the solubility of sorafenib tosylate polymorphs are important for pre-formulation and formulation studies conducted with its participation and for the safety of oncological sorafenib therapy.

Study on Typical Diarylurea Drugs or Derivatives in Cocrystallizing with Strong H-Bond Acceptor DMSO

Diarylureas are widely used in self-assembly and supramolecular chemistry owing to their outstanding characteristics as both H-bond donors and acceptors. Unfortunately, this bonding property is rarely applied in the development of urea-containing drugs. Herein, seven related dimethyl sulfoxide (DMSO) complexes were screened from 12 substrates involving sorafenib and regorafenib, mainly considering the substitution effect following a robust procedure. All complexes were structurally confirmed by spectroscopic means and thermal analysis. Specially, five cocrystals with three deuterated, named sorafenib·DMSO, donafenib·DMSO, deuregorafenib·DMSO, 6·DMSO, and 7·DMSO were obtained. The crystal structures revealed that all host molecules consistently bonded with DMSO in intermolecular interaction in a 1:1 stoichiometry. However, further comparison with documented DMSO complexes and parent motifs presented some arrangement diversities especially for 6·DMSO which offered a counter-example to previous rules. Major changes in the orientation of meta-substituents and the packing stability for sorafenib·DMSO and deuregorafenib·DMSO were rationalized by theory analysis and computational energy calculation. Cumulative data implied that the planarization of two aryl planes in diarylureas may play a crucial role in cocrystallization. Also, a polymorph study bridged the transformation between these ureas and their DMSO complexes.

Plasmon-Enhanced Controlled Drug Release from Ag-PMA Capsules

Silver (Ag)-grafted PMA (poly-methacrylic acid, sodium salt) nanocomposite loaded with sorafenib tosylate (SFT), an anticancer drug, showed good capability as a drug carrier allowing on-demand control of the dose, timing and duration of the drug release by laser irradiation stimuli. In this study, the preparation of Ag-PMA capsules loaded with SFT by using sacrificial silica microparticles as templates was reported. A high drug loading (DL%) of ∼13% and encapsulation efficiency (EE%) of about 76% were obtained. The photo-release profiles were regulated via the adjustment of light wavelength and power intensity. A significant improvement of SFT release (14% vs. 21%) by comparing SFT-Ag-PMA capsules with Ag-PMA colloids under the same experimental conditions was observed. Moreover, an increase of drug release by up to 35% was reached by tuning the laser irradiation wavelength near to Ag nanoparticles’ surface plasmon resonance (SPR). These experimental results together with more economical use of the active component suggest the potentiality of SFT-Ag-PMA capsules as a smart drug delivery system.

A Novel Halogen Bond Acceptor: 1-(4-Pyridyl)-4-Thiopyridine (PTP) Zwitterion

Sulfur is a widely used halogen bond (XB) acceptor, but only a limited number of neutral XB acceptors with bifurcated sp3-S sites have been reported. In this work a new bidentate XB acceptor, 1-(4-pyridyl)-4-thiopyridine (PTP), which combines sp3-S and sp2-N acceptor sites, is introduced. Three halogen bonded cocrystals were obtained by using 1,4-diiodobenzene (DIB), 1,4-diiodotetrafluorobenzene (DIFB), and iodopentafluorobenzene (IPFB) as XB donors and PTP as acceptor. The structures of the cocrystals showed some XB selectivity between the S and N donors in PTP. However, the limited contribution of XB to the overall molecular packing in these three cocrystals and the results from DSC measurements clearly point out the synergetic influence and interplay of all noncovalent interactions in crystal packing of these compounds.

Isomorphous Crystals Formed by the Similar Supramolecular Motifs in Sorafenib Hydrochloride and Regorafenib Hydrochloride Salts

Sorafenib and regorafenib (or fluoro-sorafenib) are multikinase inhibitors active in the treatment of various human cancers, but their solubilities are very poor. To improve their solubilities, in this study, sorafenib hydrochloride (Sor·HCl, I) and regorafenib hydrochloride (Reg·HCl, II) have been prepared and their crystal structures were characterized. Their solubility properties in water were evaluated. Intriguingly, they are isomorphous crystal structures with the same space group and the similar unit cell dimensions, which were caused by the similar supramolecular patterns resulted by the formation of N–H···Cl− hydrogen bond instead of hydrogen bond between the protonated pyridinium cation and counterion. Moreover, the solubility properties displayed identical profiles. It may be concluded that a similar crystal structure leads to a comparable solubility profile.